Field of the Invention
This invention relates to the circuit technical field, in particular to a self-adaption current control circuit.
Description of the Related Art
A current source can provide a certain direct current (DC) with stable amplitude to a load. Therefore, the current source is widely used, especially in the power supply field of light emitting diode (LED) lamps. Currently, most of DC power supplies directly convert alternating current (AC) network power into DC power with a sinusoidal ripple and output it, and it turns to be the DC with the sinusoidal ripple when being loaded on an LED lamp.
However, in the actual application, it is often required to filter the sinusoidal ripple of the current for the load. Therefore, the current is often stabilized by using a constant current control circuit having a current source filter circuit. Please refer to FIG. 1 which is a schematic diagram of an existing constant current control circuit including a current source 1, a filter capacitor 2, and an LED load 3. The LED load 3 is connected with the regulating transistor 4, the source gate of the regulating transistor 4 is connected with a sampling resistor 5, and the control gate of the regulating transistor 4 is connected with the output end of an operational amplifier 6. When the output of the current source 1 has certain fluctuation, the operational amplifier 6 controls the regulating transistor 4 through the comparison between a voltage signal on the sampling resistor 5 and a self-adaption reference voltage signal Vref, so that the current of the LED load 3 is close to constant current and equals to the input current. However, in the conventional constant current control circuit having the current source filter circuit, when the output current of the current source 1 is relatively large or small, the input voltage value of the operational amplifier 6 may exceed the appropriate input range and result in a narrower applicable current range.